EP3298647B1 - Fuel cell - Google Patents

Description

The present invention relates to the field of fuel cells, in particular the field of fuel cells suitable for use in motor vehicles.

A fuel cell allows the generation of electrical energy by an electrochemical reaction from a fuel, generally hydrogen, and an oxidizer, generally oxygen.

A solid electrolyte proton exchange membrane type fuel cell (PEMFC) usually comprises a stack of elementary cells, in the form of plates, constituting electrochemical generators, each of the cells being separated from the adjacent cells by bipolar plates. Each cell comprises an anode element and a cathode element, separated by a solid electrolyte in the form of an ion exchange membrane, made for example of a sulfurized perfluorinated polymer material. According to a usual variant embodiment, each bipolar plate provides on one side the supply of fuel to the cell adjacent to this side and on the other side the supply of oxidizer to the cell adjacent to this other side, the supplies provided. by the bipolar plates being done in parallel.

The successive stacking of the bipolar plates and the cells is maintained under support pressures which must guarantee good electrical contact and good sealing. Usually, the stack comprises rigid end plates connected by tie rods, with insertion of spring elements to limit the effects of variations in temperature and hygrometry on the support pressures. Such a solution is not, however, completely satisfactory.

Licences WO2015 / 056084 , US2005 / 0042493 , US-5993987 , US2006 / 0093890 , US2014 / 0356753 and JP 2007 329017 describe stacks of plates surrounded by portions of stretched straps.

According to one embodiment, there is provided a fuel cell which comprises a stack comprising a set of superimposed electrochemical generators, along a stacking axis, and end plates axially enclosing said assembly.

The stack further comprises at least one retaining winding surrounding said stack and resting on said end plates.

Said retaining winding comprises at least one sheet of at least one stretched wire which is wound around the stack in the form of a plurality of turns and the ends of the stretched wire of which are fixed on at least one of the plates. terminal.

Said retaining winding comprises rounded portions resting on rounded bearing portions spaced from said end plates and free portions joining these bearing portions.

Said rounded portions and said free portions of said retaining winding can advantageously meet tangentially.

Said retaining coil may extend into grooves of said end plates.

Said retaining winding may be recessed in said grooves of said end plates.

The ends of the wire forming said winding can be glued or held by wedging on said end plates.

Said end plates may have projecting tabs extending laterally from said assembly and in which said grooves extend.

The stack may include a plurality of parallel holding coils spaced perpendicular to the stacking axis.

Advantageously, the wire of said retaining winding can be made of glass fibers impregnated with a thermoset resin (CVR).

• la figure 1 représente une vue en perspective d'une pile à combustible, y compris un ensemble de générateurs électrochimiques, des plaques terminales et des enroulements de maintien ;
• la figure 2 représente une vue éclatée en perspective d'une partie de l'ensemble de générateurs électrochimiques de la figure 1 ;
• la figure 3 représente une vue en perspective d'une partie de la pile de la figure 1, l'ensemble de générateurs électrochimiques étant enlevé ;
• la figure 4 représente une coupe selon un axe d'empilage de la pile de la figure 1, passant par un enroulement de maintien ; et
• la figure 5 représente une installation de réalisation d'un enroulement de maintien de la pile de la figure 1.

A fuel cell will now be described by way of non-limiting example, illustrated by the drawing in which:

• the figure 1 shows a perspective view of a fuel cell, including an assembly of electrochemical generators, end plates and holding windings;
• the figure 2 shows an exploded perspective view of part of the set of electrochemical generators of the figure 1 ;
• the figure 3 shows a perspective view of part of the stack of the figure 1 , the set of electrochemical generators being removed;
• the figure 4 represents a section along a stacking axis of the stack of the figure 1 , passing through a retaining winding; and
• the figure 5 shows an installation for producing a winding for retaining the battery of the figure 1 .

As shown on the figure 1 , a fuel cell 1 comprises a stack 2 which consists of an assembly 3 of electrochemical generators 4 superimposed, along a stacking axis, and of end plates 5 and 6 axially enclosing the assembly 3.

As illustrated more precisely on the figure 2 , by way of example, the assembly 2 comprises a plurality of cells 7 in the form of plates, separated by bipolar plates 8. Each cell 7 comprises three superimposed layers, namely an anode, an electrolyte and a cathode. Each bipolar plate 8 provides on one side the fuel supply to the cell adjacent to this side and on the other side the supply of oxidizer to the cell adjacent to this other side. The assembly 2 comprises channels arranged so as to ensure these supplies via at least one of the end plates 5 and 6. The components external to the stack 2 of the stack 1, for hydraulic connection and electrical connection, are not used. not shown in the drawing.

The assembly 2 is in the form of a parallelepiped. The end plates 5 and 6, which are thick and rigid, protrude laterally from the assembly 2.

As shown on the figure 1 , 3 and 4 , the stack 1 comprises windings 9 of a plurality of turns, with one or more superposed layers, of at least one stretched wire wound around the stack 2, the windings 9 surrounding the stack 2 and rest on the end plates 5 and 6. These windings 9 serve to firmly hold the plates of the assembly 2 and of the end plates 5 and 6 resting on each other in order to ensure the desired seals and the desired electrical contacts. In the example shown, three windings 9 are provided and are formed parallel at a distance from each other, perpendicular to the axis of the stack 2.

Each retaining winding 9 has opposite portions 10 and 11 which are embedded in grooves 12 and 13 formed in the outer faces of the end plates 5 and 6 and has intermediate opposite lateral portions 14 and 15, free to support, which join these recessed portions 10 and 11 and which extend along the stacking axis, parallel to opposite sides 16 and 17 of the assembly 3 and at a distance from these sides.

The bottoms of the grooves 12 and 13 have respectively end portions 18, 19 and 20, 21, rounded, in the form of quarter circles, spaced with respect to the axis of the stack, and central portions 22 and 23 deeper.

Each retaining winding 9 has rounded corner portions 24, 25 and 26, 27 resting respectively on the rounded end portions 18, 19 and 20, 21 of the corresponding grooves 12 and 13. The rounded end portions 18, 19 and 20, 21 are joined by opposite intermediate portions 28 and 29, free to support, extending above the central portions of the grooves 12 and 13 and join the opposite side portions 14 and 15, free to support.

Thus, each retaining winding 9 is in the form of a rectangular annular band with rounded corners, of which the opposite intermediate portions 14 and 15, free to support, and the opposite intermediate portions 28 and 29 tangentially join the rounded portions of corners 24, 25 and 26, 27 resting on the rounded support portions 18, 19 and 20, 21 of the grooves 12 and 13.

So that the rounded bearing portions 18, 19 and 20, 21 of the grooves 12 and 13 can have sufficient radii, the end plates 5 and 6 have opposing projecting lugs 30, 31 and 32, 33 which extend laterally. to the sides 16 and 17 of the assembly 3 and in which extend the rounded end portions 18, 19 and 20, 21 of the grooves 12 and 13, these tabs also ensuring the positioning of the end plates 5 and 6 with respect to set 3.

The end portions of the wire forming each retaining coil 9 can be fixed on one of the end plates 5 and 6 or can be fixed one on the end plate 5 and the other on the end plate 6.

For example, the end portions of the wire forming each retaining coil 9 extend into auxiliary external grooves 34 and 35 of the end plate 5, opening into the groove 12, and are fixed in these grooves by an adhesive. adapted or by additional mechanical means of wedging.

Preferably, the wire constituting each retaining winding 9 is made of glass fibers impregnated with a thermoset resin, generally referred to by the abbreviation CVR. Such a material has the advantage of being resistant in traction while having a certain elasticity, so that the windings 9 make it possible to obtain the desired bearing pressures in the stack 2 and to ensure the desired seals and desired electrical contacts, mentioned above, while being able to absorb and compensate for variations in the dimensions of the stack 2, due in particular to variations in temperature and humidity.

The rounded corner portions 24, 25 and 26, 27 of each winding 9 have radii such that the wire of the winding is subjected to limited bending stresses.

As shown on the figure 5 , each holding winding 9 can be produced in the manner of a winding.

Having formed the stack 2 and now the latter provisionally for example using clamps, the stack 2 is installed on a rotating machine 36, capable of rotating the stack 2 along a median axis of rotation 37 perpendicular to the stacking axis.

The end of a wire 38 is fixed in one of the auxiliary grooves 34 or 35, this wire coming from a supply spool 39.

Stack 2 and feed spool 39 are rotated so that wire 38 winds around stack 2, engaging it in grooves 12 and 13 of end plates 5 and 6, the tension of wire 38 being provided by a counterweight 40 suspended from a pulley 41 pulling down a portion of wire 38 passing over return pulleys 42 and 43 so that this portion of wire 38 forms a U.

After having produced a layer or several superimposed layers of wire 38 around the stack 2, the wire 38 is engaged in the other auxiliary groove 34 or 35. The wire 38 is glued in this auxiliary groove and the wire 38 is cut at the bottom. - beyond this collage.

The procedure is the same to make the other retaining windings 9.

In an alternative embodiment, the retaining windings 9 can be made one after the other, the end plate 5 having connecting grooves 44 allowing the wire 38 to pass from a winding produced to the neighboring winding. achieve.

Claims (8)

1. Fuel cell comprising a stack comprising an assembly (2) of overlaid electrochemical generators, along a stack axis, and end plates (5, 6) axially clasping said assembly, the fuel cell further comprising at least one holding winding (9) surrounding said stack (2) and bearing on said end plates (5, 6),
   characterized in that said holding winding (9) comprises at least one sheet of at least on taut wire wound around the stack in the form of a plurality of turns, the ends of the taut wire being fixed on at least one of the end plates;
   and in that said holding winding (9) comprises rounded portions (24, 25, 26, 27) bearing on spaced-apart bearing rounded portions (18, 19 and 20, 21) of said end plates (5, 6) and free portions (14, 15, 28, 29) joining these bearing portions.
2. Fuel cell according to Claim 1, wherein said rounded portions and said free portions of said holding winding (9) join tangentially.
3. Fuel cell according to any one of the preceding claims, wherein said holding winding (9) extends into grooves (12, 13) of said end plates (5, 6).
4. Fuel cell according to claim 3, wherein said holding winding (9) is embedded in said grooves (12, 13) of said end plates (5, 6).
5. Fuel cell according to any one of the preceding claims, wherein the ends of the wire forming said winding (9) are glued or held by wedging on said end plates.
6. Fuel cell according to any one of claims 3 and 4, wherein said end plates have projecting tabs (30, 31, 32, 33) extending laterally with respect to said assembly (3) and into which said grooves (12, 13) extend.
7. Fuel cell according to any one of the preceding claims, comprising several parallel holding windings (9), spaced perpendicularly with respect to the stack axis.
8. Fuel cell according to any one of the preceding claims, wherein the wire of said holding winding (9) is made of glass fibres impregnated with a thermoset resin (CVR).

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